1. Field of Invention
The present invention relates to a jig for use in measuring an accuracy with which a mounting device mounts at least one member on a substrate and a method of measuring, with the jig, the accuracy.
2. Related Art Statement
Recently, there has been a strong demand to improve an accuracy with which electric components (ECs) are mounted on a printed-wiring board (PWB), so as to meet such requirements to shorten a pitch at which each EC has its lead wires and increase a density at which the ECs are mounted on the PWB. To this end, first, it is needed to measure a positional error of each EC mounted on the PWB. An example of a positional-error measuring device is disclosed in Japanese Patent Document No. 4-344411. This positional-error measuring device includes (a) a plurality of standard chips, (b) a jig on which the chips are mounted by an EC mounting device, (c) an image taking device which takes respective images of the chips mounted on the jig, and (d) a computer which compares image data representing each of the respective images of the chips taken by the image taking device, with reference image data, and determines at least one positional error of each of the chips mounted on the jig by the EC mounting device. This positional-error measuring device may be provided as an independent device for exclusive use in measuring the positional error, or as an integral portion of the EC mounting device.
The positional-error measuring device sequentially takes the respective images of the chips mounted on the jig, compares a batch of image data representing each of the taken images of the chips, with a batch of reference image data which are prepared in advance, and determines at least one positional error of each chip. The batches of image data representing the respective images of the chips are obtained by repeating (a) feeding, relative to the image taking device, the jig in a direction parallel to the opposite major surfaces of the jig and (b) taking an image of each chip being positioned at an image-take position. However, the thus measured positional error of each chip contains not only a mounting error of the EC mounting device but also a feeding error of a feeding device which feeds the jig relative to the image taking device. To solve this problem, the feeding error of the feeding device is measured in advance, and this feeding error is subtracted from the above-indicated measured positional error, to determine finally a mounting error of the EC mounting device. More specifically described, in order to measure a feeding error of the feeding device, a jig having a reference mark is prepared, and the jig is fed by the feeding device in the same manner as that in which the images of the chips are taken, so that an image of the reference mark is taken and, based on the taken image, the feeding error of the feeding device is determined. Based on this feeding error, the above-indicated measured positional error is corrected to determine finally the mounting error of the EC mounting device.
Thus, the conventional positional-error measuring device cannot help measuring a mounting error containing a feeding error and, to avoid this problem, the feeding error is measured in advance to correct the measured mounting error. Therefore, it needs a long time to finally obtain the corrected mounting error, and it is difficult to improve the accuracy of measurement of the mounting error. Moreover, since the mounting error containing the feeding error, and the feeding error itself are measured at different times, the jig used to measure the mounting error, and the jig used to measure the feeding error may be set, on the EC mounting device, at different positions, which may lead to producing a setting error which may, in turn, be contained in the above-indicated, measured positional error.
The present invention provides a jig, a standard chip, a jig set, an accuracy measuring method, an accuracy-measuring-program recording medium, and a mounting apparatus which have one or more of the following technical features that are described below in respective paragraphs given parenthesized sequential numbers (1) to (27). Any technical feature that includes another technical feature shall do so by referring, at the beginning, to the parenthesized sequential number given to the latter feature. Thus, two or more of the following features may be combined, if appropriate. Each feature may be accompanied by a supplemental explanation, as needed. However, the following features and the appropriate combinations thereof are just examples to which the present invention is by no means limited. In addition, in the case where one technical feature recites a plurality of items, it is not essentially required that all of those items be simultaneously employed. That is, it is possible to select and employ only a portion (one, two, . . . , but not all) of those items of that technical feature
(1) According to a first feature of the present invention, there is provided a jig for use in measuring an accuracy with which a mounting device mounts at least one proper member on a proper substrate, wherein the improvement comprises that the jig is set, in place of the proper substrate, on the mounting device, that at least one standard chip is mounted on the jig by the mounting device, and that the jig has at least two reference marks at respective positions which assure that respective images of the reference marks and an image of at least a portion of the standard chip mounted on the jig are simultaneously taken by a single image taking device, so that the accuracy is determined based on the images taken by the image taking device. The standard chip has the standard dimensions of the proper member and accordingly, when an image of at least a portion of the standard chip mounted on the jig is taken, the taken image can be used to determine the accuracy. Each proper member may be used as the standard chip, because each proper member should have the standard dimensions.
In the case where the standard chip is mounted on the jig according to the first feature (1) and the respective images of the reference marks of the jig and the image of the portion of the standard chip mounted on the jig are simultaneously taken by the single image taking device, at least one relative position of the standard chip relative to the jig can be determined and, based on the thus determined at least one relative position, at least one positional error of the standard chip relative to the jig can be determined. The at least one positional error may comprise at least one of respective positional errors of the chip relative to the jig along an X axis and a Y axis perpendicular to each other and an angular (i.e., rotation-positional) error of the chip relative to the jig about a Z axis perpendicular to the X and Y axes. The thus determined positional error of the chip does not contain the above-indicated feeding error that is contained in the mounting error measured by the conventional positional-error measuring device. Thus, owing to the jig according to the first feature (1), the mounting accuracy of the mounting device can be measured with high reliability or accuracy. In addition, since it is not needed to measure the feeding error in advance or remove the feeding error from the preliminarily measured mounting error, the mounting accuracy can be measured with high efficiency. Meanwhile, the mounting accuracy may be measured by an exclusive mounting-accuracy measuring device, independent of the mounting device, in such a manner that at least one standard chip is mounted on a jig set on the exclusive device. However, in the case where the mounting device is provided with the image taking device and a moving device which moves one of the image taking device and the jig relative to the other, the mounting device can measure its mounting accuracy. In this case, it is not needed to use the exclusive mounting-accuracy measuring device, which leads to reducing the cost needed to measure the mounting accuracy. Moreover, if an image of the chip is taken immediately after the chip is mounted on the jig, it is not needed to move one of the jig and the image taking device relative to the other, which leads to reducing the time needed to measure the mounting accuracy. The exclusive measuring device or the mounting device may be provided with not only to the first moving device which moves one of the jig and the image taking device relative to the other, but also a second moving device which moves one of jig and a holder which holds the chip, relative to the other. Although the first and second moving devices may be independent of each other, the two moving devices may be provided by a single moving device, which leads to reducing the cost needed to produce the exclusive measuring device or the mounting device.
(2) According to a second feature (2) of the present invention that includes the first feature (1), the jig has, at a plurality of locations, a plurality of groups of reference marks, respectively, each of which includes at least two reference marks.
In the case where the jig according to the second feature (2) is employed, a plurality of standard chips (e.g., a plurality of proper members) are mounted on the jig, such that each of the standard chips is associated with a corresponding one of the groups of reference marks, and the accuracy with which the each chip is mounted on the jig is measured. Thus, a mounting accuracy may be measured at each of the locations on the jig.
(3) According to a third feature (3) of the present invention that includes the first or second feature (1) or (2), the jig has, at at least four locations, at least four groups of reference marks, respectively, each of which includes at least two reference marks, the at least four locations comprising four corners of a mount area on the jig where the mounting device is allowed to mount the at least one standard chip.
In the case where the jig according to the third feature (3) is employed, four standard chips may be mounted on the jig, such that each of the standard chips is associated with a corresponding one of four groups of reference marks provided at four corners of the mount area on the jig, and the accuracy with which the each chip is mounted on the jig may be measured. Thus, a mounting accuracy may be measured at each of the four corners of the mount area on the jig. The respective accuracies measured for the four corners may be used to estimate a general tendency of mounting accuracy of the mounting device with respect to the entire mount area on the jig.
(4) According to a fourth feature (4) of the present invention that includes the third feature (3), the at least four groups of reference marks are provided at a regular interval of distance in the substantially entire mount area on the jig.
In the case where the jig according to the fourth feature (4) is employed, at least four standard chips are mounted on the jig, such that each of the standard chips is associated with a corresponding one of at least four groups of reference marks provided at the regular interval of distance in the entire mount area on the jig, and the accuracy with which the each chip is mounted on the jig are measured. Thus, a mounting accuracy is measured at each of the at least four locations regularly provided in the mount area on the jig. The respective accuracies measured for the regularly provided locations may be used to estimate a more reliable tendency of mounting accuracy of the mounting device with respect to the entire mount area on the jig.
(5) According to a fifth feature (5) of the present invention that includes any one of the first to fourth features (1) to (4), the mounting device comprises an electric-component mounting device which mounts at least one electric component as the at least one proper member, on a printed circuit board as the proper substrate. At least one electric component may be used as at least one standard chip that should have the standard dimensions of the electric component.
(6) According to a fifth feature of the present invention that includes any one of the first to fourth features (1) to (4), wherein the jig is formed of a material which has a linear expansion coefficient of not more than 20xc3x9710xe2x88x926. This linear expansion coefficient is expressed in terms of degrees Celsius, xc2x0 C. Though the jig may be formed of a metal having the linear expansion coefficient of not more than 20xc3x9710xe2x88x926, it is preferred that the jig be formed of a glass or a ceramics having the linear expansion coefficient of not more than 10xc3x9710xe2x88x926, more preferably of not more than 5xc3x9710xe2x88x926, and most preferably of not more than 2xc3x9710xe2x88x926.
(7) According to a seventh feature of the present invention, there is provided a standard chip for use in measuring an accuracy with which a mounting device mounts at least one proper member on a proper substrate, by setting a jig having at least two first reference marks, in place of the proper substrate, on the mounting device, wherein the improvement comprises that at least one the standard chip is mounted on the jig by the mounting device, that the standard chip has at least one positioning reference portion which is utilized by the mounting device to position the standard chip relative to the jig, when the standard chip is mounted on the jig by the mounting device, and that the standard chip has at least one second reference mark at at least one position which assures that respective images of the first reference marks of the jig and an image of the second reference mark of the standard chip mounted on the jig are simultaneously taken by an image taking device, so that the accuracy is determined based on the images taken by the image taking device.
In the case where at least one standard chip according to the seventh feature (7) is mounted on the jig according to any one of the first to sixth features (1) to (6) and the respective images of the first reference marks of the jig and the second reference mark of the standard chip mounted on the jig are simultaneously taken, the taken images can be used to determine the mounting accuracy which is not influenced by the above-indicated feeding error that is contained in the mounting error measured by the conventional positional-error measuring device. At least one proper member may be used as at least one standard chip. However, the dimensional tolerances of the proper member such as an EC are considerably large and accordingly, in the case where at least one proper member or EC is mounted as at least one standard chip on the jig to measure the mounting accuracy of the mounting device, the measured mounting accuracy may contain the dimensional errors of the proper member or EC. To avoid this problem, it is preferred to use at least one exclusive standard chip which is formed with negligible, small errors. The positioning reference portion and the second reference mark may be independent of each other, or may be integral with each other.
(8) According to an eighth feature (8) of the present invention that includes the seventh feature (7), the standard chip has a light-transmitting portion which enables the image taking device to take, in a state in which the standard chip is mounted on the jig, the images of the first reference marks of the jig through the light-transmitting portion of the standard chip.
The standard chip according to the eighth feature (8) includes the light-transmitting portion. Accordingly, in the case where the first reference marks of the jig underlie the standard chip, the image taking device can simultaneously take the respective images of the first and second reference marks. The standard chip may have its light-transmitting portion as only a portion thereof which is opposed to the first reference marks of the jig when the chip is mounted on the jig. Alternatively, the standard chip may have its light-transmitting portion as the remaining portion other than the positioning reference portion and the second reference mark.
(9) According to a ninth feature (9) of the present invention that includes the eighth feature (8), the light-transmitting portion of the standard chip is formed of a transparent material.
Alternatively, the light-transmitting portion of the standard chip may be defined by an opening which is formed through the thickness of the chip. However, in the case where the standard chip according to the ninth feature (9) is used, the chip may be entirely formed of the transparent material, and a standard icon which enables an image taking device to take n image thereof which is substantially identical with that of the proper member may be provided on one of opposite major surfaces of the transparent chip. In this case, standard chips can be easily and accurately mass-produced.
(10) According to a tenth feature (10) of the present invention that includes any one of the seventh to ninth features (7) to (9), the positioning reference portion of the standard chip comprises a standard icon which enables an image taking device to take an image of the standard icon which is substantially identical with an image, taken by the image taking device, of a positioning reference portion of the proper member.
In the case where the standard chip according to the tenth feature (10) is mounted on the jig in the same mounting operation as that carried out to mount the proper member on the proper substrate, the mounting accuracy of the mounting operation can be measured. The standard icon may be one which represents at least a portion of the proper member that is needed to position the chip relative to the jig.
(11) According to an eleventh feature (11) of the present invention that includes the tenth feature (10), the standard icon has an outline which enables the image taking device to take an image of the outline which is substantially identical with an image, taken by the image taking device, of a plurality of lead wires projecting laterally from at least one side surface of an electric component as the proper member.
(12) According to a twelfth feature (12) of the present invention that includes any one of the eighth to eleventh features (8) to (11), the standard chip has the second reference mark at the position in the light-transmitting portion thereof, such that the second reference mark of the standard chip mounted on the jig does not overlap the first reference marks of the jig.
In the case where the standard chip according to the twelfth feature (12) is mounted on the jig, the image taking device can take the respective images of the first and second reference marks in the area of the light-transmitting portion.
(13) According to a thirteenth feature (13) of the present invention that includes the twelfth feature (12), the standard chip has the light-transmitting portion thereof inside the positioning reference portion thereof.
In the case where the positioning reference portion of the standard chip is sufficiently large, the chip can have its light-transmitting portion inside its positioning reference portion.
(14) According to a fourteenth feature (14) of the present invention that includes the twelfth feature (12), the standard chip has the light-transmitting portion thereof outside the positioning reference portion thereof.
(15) According to a fifteenth feature (15) of the present invention that includes any one of the seventh to fourteenth features (7) to (14), the standard chip has the second reference mark in the positioning reference portion thereof, at the position which assures that the respective images of the first reference marks of the jig and the image of the second reference mark of the standard chip mounted on the jig are simultaneously taken by the image taking device.
The standard chip according to the fifteenth feature (15) just requires that the second reference mark should have an optical characteristic, such as a color or a brightness, different from that of the positioning reference portion as the background of the second reference mark. For example, in the case where the positioning reference portion is black, the second reference mark may be white, yellow, or transparent. Alternatively, the positioning reference portion may be provided by the light-transmitting portion which is formed of a transparent material, and the background of the transparent positioning reference portion and the second reference mark may be black.
(16) According to a sixteenth feature (16) of the present invention that includes any one of the seventh to fifteenth features (7) to (15), the second reference mark of the standard chip has a rectangular shape.
In the case where the standard chip has only one second reference mark which is rectangular or elongate, an angular error of the chip relative to the jig about an axis line such as a vertical axis line can be measured based on the respective images of the first and second reference marks. The second reference mark may be a standard icon which enables an image taking device to take an image thereof which is identical is with that of the proper member.
(17) According to a seventeenth feature (17) of the present invention that includes any one of the seventh to fifteenth features (7) to (15), the second reference mark of the standard chip has a circular shape.
(18) According to an eighteenth feature (18) of the present invention that includes the seventeenth features (17), the standard chip has a plurality of second reference marks each of which has a circular shape.
Since the standard chip according to the eighteenth feature (18) has a plurality of circular second reference marks, not only respective positional errors of the chip relative to the jig in an X-axis and a Y-axis direction perpendicular to each other on a horizontal plane, but also an angular error of the chip relative to the jig about a vertical axis line can be measured, though each second reference mark is circular. The respective images of the second reference marks and the at least two first reference marks may be simultaneously taken by the single image taking device. However, alternatively, respective images of a portion (e.g., one) of the second marks and at least one first reference mark may be taken. In the latter case, it is preferred that at least two groups of first and second reference marks be taken.
(19) According to a nineteenth feature (19) of the present invention that includes any one of the seventh to eighteenth features (7) to (18), the standard chip is formed of a material which has a linear expansion coefficient of not more than 20xc3x9710xe2x88x926.
Though the standard chip may be formed of a metal having the linear expansion coefficient of not more than 20xc3x9710xe2x88x926, it is preferred that the chip be formed of a glass or a ceramics having the linear expansion coefficient of not more than 10xc3x9710xe2x88x926, more preferably of not more than 5xc3x9710xe2x88x926, and most preferably of not more than 2xc3x9710xe2x88x926.
(20) According to a twentieth feature (20) of the present invention, there is provided a jig set for use in measuring an accuracy with which a mounting device mounts at least one proper member on a proper substrate, the jig set comprising a jig which is adapted to be set, in place of the proper substrate, on the mounting device; and at least one standard chip which is mounted on the jig by the mounting device, the jig having at least two reference marks at respective positions which assure that respective images of the reference marks and an image of at least a portion of the standard chip mounted on the jig are simultaneously taken by an image taking device, so that the accuracy is determined based on the images taken by the image taking device.
In the case where the jig set according to the twentieth feature (20) is used to measure the mounting accuracy, it is preferred to present, when an image of the standard chip mounted on the jig is taken, a good contrast between the chip and the jig by making, e.g., the chip black and the jig white, yellow, or transparent. The jig according to any one of the first to sixth features (1) to (6) and the standard chip according to any one of the seventh to nineteenth features (7) to (19) may be combined, as needed, to provide the jig set according to the twentieth feature (20).
(21) According to a twenty-first feature (21) of the present invention, there is provided a method of measuring an accuracy with which a mounting device mounts at least one proper member on a proper substrate, the method comprising the steps of mounting, with the mounting device, at least one proper member on a jig according to any one of the first to sixth features (1) to (6), simultaneously taking, with an image taking device, respective images of the reference marks of the jig and an image of at least a portion of the proper member mounted on the jig, and processing, with an image-data processing device, image data representing the images taken by the image taking device, to determine respective relative positions of the proper member relative to the reference marks of the jig and determine, based on the determined relative positions, at least one positional error of the proper member mounted on the jig by the mounting device.
In the mounting-accuracy measuring method according to the twenty-first feature (21), the mounting accuracy of the mounting device can be easily and accurately measured by using the jig. In particular, in the case where the image-taking step is carried out by utilizing the image-taking device which is employed for a different purpose in the mounting device, the mounting device need not employ any additional elements for measuring its mounting accuracy. However, the image-data processing device needs a modified control software or program for processing the image data representing the images taken by the image taking device.
(22) According to a twenty-second feature (22) of the present invention, there is provided a method of measuring an accuracy with which a mounting device mounts at least one proper member on a proper substrate, the method comprising the steps of mounting, with the mounting device, at least one standard chip according to any one of the seventh to nineteenth features (7) to (19), on a jig according to any one of the first to sixth features (1) to (6), simultaneously taking, with an image taking device, respective images of the reference marks of the jig as first reference marks and an image of the second reference mark of the standard chip mounted on the jig, and processing, with an image-data processing device, image data representing the images taken by the image taking device, to determine respective relative positions of the second reference mark relative to the first reference marks of the jig and determine, based on the determined relative positions, at least one positional error of the standard chip mounted on the jig by the mounting device.
(23) According to a twenty-third feature (23) of the present invention, there is provided a recording medium in which an accuracy measuring program is recorded such that the program is readable by a computer, the program comprising the steps of controlling the mounting device to mount at least one standard chip on a jig according to any one of the first to sixth features (1) to (6)), controlling a single image taking device to take simultaneously respective images of the reference marks of the jig and an image of at least a portion of the standard chip mounted on the jig, and controlling an image-data processing device to process image data representing the images taken by the image taking device, to determine respective relative positions of the standard chip relative to the reference marks of the jig and determine, based on the determined relative positions, at least one positional error of the standard chip mounted on the jig by the mounting device.
In the case where the accuracy measuring program according to the twenty-third feature (23) is entirely carried out by the mounting device, the mounting device can measure its own mounting accuracy. That is, in the case where the present program is carried out by any sort of conventional mounting device, the mounting device can measure its own mounting accuracy. The thus measured mounting accuracy may be used to evaluate the overall accuracy of the mounting device or to adjust the various parameters used in the mounting device.
(24) According to a twenty-fourth feature (24) of the present invention that includes the twenty-third feature (23), the step of controlling the mounting device comprises controlling the mounting device to mount at least one standard chip according to any one of the seventh to nineteenth features (7) to (19), on the jig, the step of controlling the image taking device comprises controlling the image taking device to take simultaneously respective images of the reference marks of the jig as first reference marks and an image of the second reference mark of the standard chip mounted on the jig, and the step of controlling the image-data processing device comprises controlling the image-data processing device to processes image data representing the images taken by the image taking device, to determine respective relative positions of the second reference mark relative to the first reference marks of the jig and determine, based on the determined relative positions, at least one positional error of the standard chip mounted on the jig by the mounting device.
(25) According to a twenty-fifth feature (25) of the present invention, there is provided a mounting apparatus for mounting at least one proper member on a proper substrate, comprising at least one holder which holds the at least one proper member; a supporting device which supports the proper substrate; a first moving device which moves at least one of the holder and the supporting device relative to the other of the holder and the supporting device; a control device which controls, according to prescribed control data, the first moving device so that the proper member held by the holder is mounted on the proper substrate supported by the supporting device; an image taking device having a field of view through which the image taking device can take an image of a local portion of the proper substrate supported by the supporting device; a second moving device which moves at least one of the supporting device and the image taking device relative to the other of the supporting device and the image taking device; a jig which is supported, in place of the proper substrate, by the supporting device, so that at least one standard chip, held by the at least one holder, is mounted on the jig, the jig having at least two reference marks at respective positions which assure that respective images of the reference marks and an image of at least a portion of the standard chip mounted on the jig are simultaneously taken by the image taking device; an image-data processing device which processes image data representing the images taken by the image taking device, and determines at least one positional error of the standard chip mounted on the jig by the mounting device; and a correcting device which corrects the prescribed control data based on the at least one positional error determined by the image-data processing device.
Since the mounting apparatus according to the twenty-fifth feature (25) carries out the mounting operation while correcting the control data based on the measured positional error, the mounting apparatus can mount, with high accuracy, the proper member or members on the proper substrate. The positional error is mainly caused by the error of actual movement amount produced by the first moving device which is controlled by the control device according to the control data. However, since the control data are corrected by the correcting device based on the measured positional error, the control device can control the first moving device according to the thus corrected control data. In the case where the present mounting device has an additional function of measuring, with an image taking device, at least one positional error of the standard chip held by the holder and correcting the control data based on the thus measured positional error of the chip held by the holder, the above-indicated positional error of the chip mounted on the jig may contain an error which is caused by the general characteristic of this function. In the latter case, therefore, the error caused by the general characteristic of the function can be reduced by correcting the control data based on the measured positional error of the chip mounted on the jig. The present mounting apparatus may carry out, in advance, an accuracy measuring operation in which at least one standard chip is mounted on each of a plurality of sorts of jigs corresponding to a plurality of sorts of proper substrates, so as to measure a positional error of the chip mounted on the each sort of jig, or obtain a correction amount for correcting the positional error. Alternatively, immediately before the mounting apparatus starts a mounting operation in which at least one proper member is mounted on each sort of proper substrate, the mounting apparatus may carry out an accuracy measuring operation in which a jig corresponding to the each sort of proper substrate is used. Moreover, the mounting apparatus may carry out an accuracy measuring operation each time proper members are successively mounted on a predetermined number of proper substrates. While the mounting apparatus may carry out an accuracy measuring operation in which a jig corresponding to each sort of proper substrate is used, the mounting apparatus may carry out an accuracy measuring operation to determine its general mounting-error tendency and correct, based on the thus determined mounting-error tendency, the control data prescribed for each sort of proper substrate.
(26) According to a twenty-fifth feature (26) of the present invention that includes the twenty-fifth feature (25), the mounting apparatus further comprises a memory which stores the at least one positional error determined by the image-data processing device, and the correcting device corrects the prescribed control data based on the positional error stored in the memory.
(27) According to a twenty-seventh feature (27) of the present invention that includes the twenty-fifth feature (25), the mounting apparatus further comprises a correction-amount determining device which determines, based on the at least one positional error determined by the image-data processing device, at least one correction amount for correcting the at least one positional error; and a memory which stores the at least one correction amount determined by the correction-amount determining device, and the correcting device corrects the prescribed control data based on the correction amount stored in the memory.